<meta charset="utf-8">
(#) Use the 'require_____()' API rather than 'get____()' API for more descriptive error messages when it's null

!!! ERROR: Use the 'require_____()' API rather than 'get____()' API for more descriptive error messages when it's null
   This is an error.

Id
:   `UseRequireInsteadOfGet`
Summary
:   Use the 'require_____()' API rather than 'get____()' API for more descriptive error messages when it's null
Severity
:   Error
Category
:   Correctness
Platform
:   Any
Vendor
:   Android Open Source Project
Identifier
:   androidx.fragment
Feedback
:   https://issuetracker.google.com/issues/new?component=460964
Min
:   Lint 7.0
Compiled
:   Lint 8.0 and 8.1
Artifact
:   [androidx.fragment:fragment](androidx_fragment_fragment.md.html)
Since
:   1.2.2
Affects
:   Kotlin and Java files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/fragment/fragment-lint/src/main/java/androidx/fragment/lint/UseRequireInsteadOfGet.kt)
Tests
:   [Source Code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/fragment/fragment-lint/src/test/java/androidx/fragment/lint/UseRequireInsteadOfGetTest.kt)
Copyright Year
:   2020

AndroidX added new "require____()" versions of common "get___()" APIs,
such as getContext/getActivity/getArguments/etc. Rather than wrap these
in something like requireNotNull(), using these APIs will allow the
underlying component to try to tell you _why_ it was null, and thus
yield a better error message.

!!! Tip
   This lint check has an associated quickfix available in the IDE.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/foo/Test.java:10:Error: Use fragment.requireArguments() instead of
checkNotNull(fragment.getArguments()) [UseRequireInsteadOfGet]
    checkNotNull(fragment.getArguments());
    -------------------------------------
src/foo/Test.java:11:Error: Use fragment.requireFragmentManager()
instead of checkNotNull(fragment.getFragmentManager())
[UseRequireInsteadOfGet]
    checkNotNull(fragment.getFragmentManager());
    -------------------------------------------
src/foo/Test.java:12:Error: Use fragment.requireContext() instead of
checkNotNull(fragment.getContext()) [UseRequireInsteadOfGet]
    checkNotNull(fragment.getContext());
    -----------------------------------
src/foo/Test.java:13:Error: Use fragment.requireActivity() instead of
checkNotNull(fragment.getActivity()) [UseRequireInsteadOfGet]
    checkNotNull(fragment.getActivity());
    ------------------------------------
src/foo/Test.java:14:Error: Use fragment.requireHost() instead of
checkNotNull(fragment.getHost()) [UseRequireInsteadOfGet]
    checkNotNull(fragment.getHost());
    --------------------------------
src/foo/Test.java:15:Error: Use fragment.requireParentFragment() instead
of checkNotNull(fragment.getParentFragment()) [UseRequireInsteadOfGet]
    checkNotNull(fragment.getParentFragment());
    ------------------------------------------
src/foo/Test.java:16:Error: Use fragment.requireView() instead of
checkNotNull(fragment.getView()) [UseRequireInsteadOfGet]
    checkNotNull(fragment.getView());
    --------------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here are the relevant source files:

`src/util/Preconditions.java`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers
package util;

public final class Preconditions {
  public static <T> T checkNotNull(T value) {

  }

  public static <T> T checkNotNull(T value, String message) {

  }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

`src/foo/Test.java`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~java linenumbers
package foo;

import androidx.fragment.app.Fragment;
import static util.Preconditions.checkNotNull;

class Test {
  void test() {
    Fragment fragment = new Fragment();

    checkNotNull(fragment.getArguments());
    checkNotNull(fragment.getFragmentManager());
    checkNotNull(fragment.getContext());
    checkNotNull(fragment.getActivity());
    checkNotNull(fragment.getHost());
    checkNotNull(fragment.getParentFragment());
    checkNotNull(fragment.getView());

    // These are redundant. Java-only really
    checkNotNull(fragment.requireArguments());
    checkNotNull(fragment.requireFragmentManager());
    checkNotNull(fragment.requireContext());
    checkNotNull(fragment.requireActivity());
    checkNotNull(fragment.requireHost());
    checkNotNull(fragment.requireParentFragment());
    checkNotNull(fragment.requireView());

    // These don't have errors
    fragment.requireArguments();
    fragment.requireFragmentManager();
    fragment.requireContext();
    fragment.requireActivity();
    fragment.requireHost();
    fragment.requireParentFragment();
    fragment.requireView();

    // These are ignored because they have custom error messages
    checkNotNull(fragment.getArguments(), "getArguments");
    checkNotNull(fragment.getFragmentManager(), "getFragmentManager");
    checkNotNull(fragment.getContext(), "getContext");
    checkNotNull(fragment.getActivity(), "getActivity");
    checkNotNull(fragment.getHost(), "getHost");
    checkNotNull(fragment.getParentFragment(), "getParentFragment");
    checkNotNull(fragment.getView(), "getView");
  }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:/fragment/fragment-lint/src/test/java/androidx/fragment/lint/UseRequireInsteadOfGetTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `UseRequireInsteadOfGet.simple java checks where the fragment is a variable`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=460964.

(##) Including

!!!
   This is not a built-in check. To include it, add the below dependency
   to your project.

```
// build.gradle.kts
implementation("androidx.fragment:fragment:1.8.5")

// build.gradle
implementation 'androidx.fragment:fragment:1.8.5'

// build.gradle.kts with version catalogs:
implementation(libs.fragment)

# libs.versions.toml
[versions]
fragment = "1.8.5"
[libraries]
# For clarity and text wrapping purposes the following declaration is
# shown split up across lines, but in TOML it needs to be on a single
# line (see https://github.com/toml-lang/toml/issues/516) so adjust
# when pasting into libs.versions.toml:
fragment = {
    module = "androidx.fragment:fragment",
    version.ref = "fragment"
}
```

1.8.5 is the version this documentation was generated from;
there may be newer versions available.

[Additional details about androidx.fragment:fragment](androidx_fragment_fragment.md.html).
(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("UseRequireInsteadOfGet")
  fun method() {
     problematicStatement()
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("UseRequireInsteadOfGet")
  void method() {
     problematicStatement();
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection UseRequireInsteadOfGet
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="UseRequireInsteadOfGet" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'UseRequireInsteadOfGet'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore UseRequireInsteadOfGet ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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